Racquet for ball sports and method for manufacturing

The present invention relates to a racket for ball games, in particular a tennis, squash, badminton, racquetball or paddle tennis racket with excellent handling characteristics, as well as a manufacturing method for such a racket.

Such clubs typically include a frame that forms a club head and a handle portion connected thereto. Typically, a so-called heart region is formed in the transition region between the club head and the grip section. Typically, the frame is formed from a frame profile that is often made from a carbon fiber reinforced plastic material in a molding press. The club head of the racket defines a clothing plane in which the clothing of the racket is placed. To accommodate the sides of the clothing lying on the frame in the stringing plane through holes are provided for the implementation of clothing pages.

Moreover, it is known to provide at different points of the frame from each other different cross-sectional shapes of the frame profile, for example, to be able to provide relatively light clubs. From other points of view, it may be advantageous to provide frame profiles with varying cross-sectional shapes along the frame.

For example, EP 0 676 222 B1 discloses a racket with a handle and a frame having a head portion, force reinforcing portions and flexible portions alternately formed along the entire frame or along a portion of the frame spaced from the handle. Each force amplifying portion is formed by a projecting frame portion having a relatively large side thickness measured in a direction perpendicular to the plane of the frame. Each of the flexible portions is formed by a recessed frame portion having a relatively small side thickness measured in a direction perpendicular to the plane of the frame. The number of protruding force increasing sections is 10 to 20, and the number of recessed flexible sections is also 10 to 20. The purpose of this club construction is to eliminate the inadequate acceleration capability of a club of conventional design of the classic type and the inadequate flexibility of a conventional wide-body club.

DE 37 16 708 A1 discloses a racket with a head portion which is connected via a neck portion having a portion with a handle. The neck portion has a plurality of recesses on each of its upper and lower surfaces extending substantially parallel to the face of the head portion. These recesses are symmetrical and equidistant from each other.

The present invention has for its object to provide an improved racket, which allows excellent ball guidance and acceleration and can be constructed at the same time in lightweight construction. This object is achieved with a racket having the features of independent claim 1. In the dependent claims preferred embodiments of the racket according to the invention are described. The independent method claim 13 relates to a manufacturing method for such a racket. The dependent claims relate to advantageous embodiments of the method according to the invention.

The racquet for ball games according to the invention has a frame formed from a frame or hollow profile, which has a club head and a preferably connected thereto via a heart region grip portion. The clubhead defines a stringing plane. The frame profile has four trough-shaped indentations, which are each arranged in pairs opposite and symmetrical to the longitudinal axis of the racket.

The trough-shaped indentations are preferably arranged on the frame profile such that a cross-sectional constriction or constriction results in a direction perpendicular to the clothing plane of the racket.

The head shape of the racket is largely arbitrary and may for example be oval, egg-shaped, teardrop-shaped, rectangular with rounded corners. To define the respective position of the trough-shaped indentations along the circumference of the club head usually a dial of a clock is used, with the 12 o'clock position at the extreme or free end of the club head is arranged (see. FIG. 1). The 3 o'clock or 9 Clock position is therefore approximately in the middle of the total length of the club head.

Preferably, the four trough-shaped indentations are arranged on the club head such that a first pair is provided between 2 o'clock and 4 o'clock, in particular at about 3 o'clock, and a second pair between 8 o'clock and 10 o'clock, in particular at about 9 o'clock. The trough-shaped indentations are accordingly spaced about as far from the handle end of the racket as the center of the club face or the area of ​​the clubface with maximum impact speed. Under certain circumstances, this preferred position for the trough-shaped indentations also about 1 cm to 4 cm, preferably 2 cm to 3 cm, be moved from the center in the direction of the free end of the club head.

The racket according to the invention thus has per racket side (front or back) on two trough-shaped indentations, one of which is located on this side and the other beyond the longitudinal axis of the racket. In other words, each racket side and racket half each have a single trough-shaped indentation - thus a total of exactly four indentations - provided on the racket according to the invention. Preferably, the indentations are in the range at about 3 o'clock or 9 Clock arranged. It is thus preferred to provide in each case a pair of trough-shaped indentations in the range between 2 o'clock and 4 o'clock, in particular at approximately 3 o'clock, and another pair of trough-shaped indentations between 8 o'clock and 10 o'clock, in particular at approximately 9 o'clock the trough-shaped recesses are arranged in pairs opposite and symmetrical to the longitudinal axis of the racket.

The cross-sectional constriction caused by the trough-shaped recesses arranged opposite the frame profile is preferably such that the frame height (in the direction perpendicular to the clothing plane) is about 60 to 95%, more preferably 70 to 90%, and even more preferably about 80% of the height of Frame profile outside the indentations amounts. The length of the recess along the frame is preferably in the range between 10 mm and 30 mm, more preferably between 12 mm and 25 mm, most preferably between 15 mm and 23 mm. The trough-shaped indentations preferably have a substantially circular arc-shaped cross section, viewed in the clothing plane, which, for example, has a radius of approximately 15 mm to 25 mm, more preferably approximately 20 mm. The cross section may also be elliptical, hyperbolic, polygonal or rectangular with rounded corners.

The racket according to the invention is particularly advantageous in terms of its improved ball guidance. In addition, vibrations that occur when hitting the ball, derived less to the handle than in known rackets. At the same time, however, the acceleration capacity that can be transferred to the ball with the racket according to the invention is improved. The advantageous properties of the racket according to the invention are presumably due to the fact that the bending resistance moment of the frame profile is locally reduced by the trough-shaped indentations, so that a kind of "joint" ("control point") is created by these indentations.

As already mentioned above, the effect according to the invention is particularly advantageously recognizable if in each case a pair of trough-shaped indentations in the range between 2 o'clock and 4 o'clock, in particular at about 3 o'clock, and another pair of trough-shaped indentations between 8 o'clock and 10 o'clock, in particular at about 9 o'clock, is provided, wherein the trough-shaped recesses are preferably arranged opposite and symmetrical to the longitudinal axis of the racket. The indentations at about 3 o'clock and 9 o'clock are where the ball is hit very often during play (based on the clubface), so that the club virtually surrounds the ball by the local reduction of the bending resistance moment of the frame profile effected in the area of ​​the indentations ". This has in particular a longer residence time of the ball on the fabric of the racket and thus an improved ball control result.

The effect according to the invention can be further enhanced by providing at least one opening extending through the frame profile in the region of the trough-shaped indentations, which opening runs essentially perpendicular to the clothing plane. Preferably, the opening extends through the pairs of oppositely arranged trough-shaped indentations. In symmetrical arrangements of two openings thus each trough-shaped indentation has ever a hole, so that in this area the outermost wall of the frame profile, ie the part of the wall of the frame profile which is furthest from the clothing plane, is substantially weakened, whereby the bending resistance moment of the frame profile is further reduced.

Such a weakening of the frame profile has hitherto been considered unrealisable, since it was assumed that this would inevitably result in the frame breaking at the loads occurring during play. However, it has been shown that not only a particularly good ball guidance is possible by the indentations and possibly openings, but at the same time the required stability of the racket remains guaranteed.

The trough-shaped recesses are preferably formed during the shaping of the racket in the molding press. The optional openings are preferably formed after forming the racket in the molding press subsequently to the frame. However, they may also be made during the molding process by, for example, inserting a core into the mold. The subsequent training is preferably carried out by drilling, milling or sawing.

The cross section of the opening is usually circular in the case of drilling, but may also have any other shape. A circular opening preferably has a diameter in the range between 2 mm and 8 mm, more preferably between 3 mm and 6 mm. In an opening formed by milling or sawing usually the two opposite holes are generated in the frame profile independently of each other, each of the holes is preferably formed in the direction of view parallel to the fabric plane substantially arcuate or trough-shaped. However, it is possible to any other form for the holes. The length of each of the holes along the frame is preferably in the range between 1 mm and 10 mm, more preferably between about 3 mm and 7 mm. The depth of each hole is at least the wall thickness of the frame profile.

The width of the holes, ie their dimension in the direction of the side through holes or perpendicular to the direction of the frame at the relevant point, is preferably in the range between 3 mm and 7 mm. The dimensions of the hole, in particular its width and depth, should be selected so that the hole does not extend to a provided in the frame groove for receiving a headband.

Analogous to the trough-shaped recesses, the openings are preferably provided in pairs substantially symmetrically to the longitudinal axis of the racket, ie there may be two, four, six or more openings symmetrical to the longitudinal axis of the racket. The at least one opening is preferably in the range between 2 o'clock and 4 o'clock and / or between 8 o'clock and 10 o'clock at the club head. Particularly preferred is the paired arrangement of openings in this area. More preferably, at least one pair of apertures will be at about 3 o'clock respectively. 9 Clock provided on the club head. Furthermore, it may be advantageous to provide a plurality of openings on each side, for example, a plurality of openings symmetrically around the 3 o'clock or 9 Clock position or starting from 3 o'clock or 9 Clock towards the handle section or starting from 3 o'clock or 9 Clock to the free end of the club head to be arranged. Preferably, one through opening is central or centrally provided by a pair of opposite trough-shaped indentations.

In order to prevent the penetration of dirt and / or moisture into the frame profile, it is preferred to equip the opening with an insert, so that the frame profile is closed inwards. Preferably, the insert is tubular with a through hole formed; However, it can also be provided as a full element. The insert is usually made of an elastic material (eg Rubber), so that the advantageous effects achieved by providing the openings are influenced as little as possible. It is also possible to cover each of the holes forming the opening with a separate cover made of an elastic material, whereby the same effect is achieved.

Furthermore, it may be preferable to reinforce the frame profile in the region of the indentations and the optional openings by the provision of reinforcing layers. For this purpose, reinforcing layers of carbon fiber, glass or aramid fabric and / or a unidirectional prepreg are particularly suitable, which are arranged at an angle of ± 45 ° to the longitudinal extent of the frame profile (ie helically in the wall of the frame profile).

The racket according to the invention will now be described by way of example with reference to preferred embodiments with reference to the drawings. Show it:<dl id="dl0001" compact="compact"><dt>Fig. 1</dt><dd>a schematic front view of a racket according to the invention, in which a dial for indicating the respective frame positions is located;</dd><dt>Fig. 2a</dt><dd>an enlarged view in perspective view of a portion of the frame of a racket according to the invention with trough-shaped indentation;</dd><dt>Fig. 2b</dt><dd>an enlarged view in perspective view of a portion of the frame of a racket according to the invention with trough-shaped indentation and the optional opening;</dd><dt>Fig. 3</dt><dd>a schematic side view (view in the clothing plane) on the frame of a racket according to the invention in the region of the trough-shaped indentations;</dd><dt>Fig. 4</dt><dd>a schematic cross-sectional view of the frame profile of a racket according to the invention according to the embodiment shown in Figure 2;</dd><dt>Fig. 5</dt><dd>a sectional perspective view of the frame profile of a racket according to the invention with trough-shaped indentations and the optional opening;</dd><dt>Fig. 6a and 6b</dt><dd>Charts showing the relative speed values ​​above the frame position for a racket according to the invention and for conventional rackets; and</dd><dt>Fig. 7a and 7b</dt><dd>Charts showing the contact time of the ball with the racket above the frame position for a racket according to the invention and for conventional rackets.</dd></dl>

The schematic representation of the racket 2 according to the invention shown in Fig. 1 includes for better understanding a dial corresponding to a normal clock, wherein the 12 o'clock position (XII) is provided at the outermost free end of the racket.

The racket 2 according to the invention has a frame 4 which forms a racket head 6 and a handle section 10 preferably connected thereto via a heart area 8. The frame 4 is made of a frame or Hollow profile formed (see FIG. 4). The club head defines a clothing plane of the racket. For receiving the clothing, the frame 4 in the region of the club head 6 has a plurality of through holes 7 lying substantially in the clothing plane (FIG. 3) for the performance of stringed strings 9, of which in the cross section of FIG. 4 one is shown schematically.

According to the frame profile is generally between about 2 o'clock and 4 o'clock, in particular at about 3 o'clock, or between about 8 o'clock and 10 o'clock, in particular at about 9 o'clock, in each case a pair of opposite trough-shaped indentations 12 are provided. Thus, a total of four of the recesses 12 are formed on the racket 2 according to the invention. Due to the recesses 12, the frame height in the direction perpendicular to the clothing plane in this area is reduced by twice the amount T of each trough-shaped indentation 12. The depths T of the opposing recesses 12 are preferably dimensioned such that in the region of the indentations a frame height h results which is approximately 60 to 95%, preferably approximately 70 to 90%, more preferably approximately 80%, of the frame height H outside the indentations 12 is. Consequently, the racket according to the invention, for example, at a frame height H of 20 mm in the region of the opposing recesses 12 a frame height h of about 16 mm.

The length L of the trough-shaped recesses along the frame is typically in the range of 10 mm to 30 mm, preferably between 12 mm and 25 mm, and more preferably between 15 mm and 23 mm. It is further preferred to form the trough-shaped indentation 12 substantially in the form of a circular arc when viewed in the clothing plane, with radii R in the range between 15 mm and 25 mm being preferred. A radius of about 20 mm is currently particularly preferred.

The width B of the trough-shaped indentation, ie its dimension in the direction of the string through-holes or perpendicular to the direction of the frame at the relevant point, depends essentially on the cross-sectional shape of the frame profile and the depth T of the indentation 12. However, the trough-shaped recesses 12 typically extend substantially over the entire width of the frame profile.

For a racket with a frame height H of 19 mm and a radius of the trough-shaped recess of 20 mm results in a trough length L of about 17 mm and a case depth T of about 1.9 mm, so that the frame height h in the region of the opposite recesses 12 is about 15.2 mm, ie about 80% of the frame height H. For a racket with a frame height H of 28.5 mm results in the same radius for the trough-shaped indentations a trough length L of about 20.6 mm and a bowl depth of about 2.85 mm. The remaining frame height h in the region of the indentations 12 is thus about 22.8 mm, which also corresponds to a reduction of the frame height to 80% of the lying outside of the recesses 12 frame height H.

In Fig. 2a, a recess 12 on the frame 4 of the racket according to the invention is shown in more detail.

In the embodiment of the racket 2 according to the invention shown in FIGS. 2 b, 4 and 5, an optional opening 14 is furthermore provided in the trough 12, which is substantially perpendicular to the clothing plane or extends to the through holes 7 for the stringed strings 9 through the frame profile to the opposite trough 12, preferably centrally through the troughs. The opening 14 is, as shown in FIG. 2b, formed in the form of a substantially circular cylindrical through hole. The bore extends through the two opposite walls of the frame profile, thereby forming two opposite, aligned holes in the frame profile. The diameter of the opening is preferably in the range between about 2 mm and 8 mm, more preferably between 3 mm and 6 mm.

To avoid the entry of dirt and / or moisture into the interior of the frame profile, an insert 16 is preferably provided in the opening 14, which terminates the frame profile to the interior of the opening 14. The insert 16 is preferably tubular, ie with a passage opening 18, formed. However, it can also be designed as a "lid" or solid profile. The insert 16 is typically made of a soft, resilient material so that it does not significantly affect the characteristics of the racquet in this area. Preference is given to a transparent plastic (eg Rubber). The tubular insert 16 preferably has a small wall thickness of, for example about 0.5 to 1.5 mm, preferably from about 0.5 to 1 mm, on.

Another way to provide the opening 14 in the frame 4 of the racket 2 according to the invention, is instead of a through hole through the frame profile at the front and back of the frame each form individual holes. As already mentioned above, two opposite holes together form an opening 14 extending through the frame profile. The holes may have any desired shape, but are preferably substantially arcuate or trough-shaped in the viewing direction parallel to the clothing plane. This can be realized for example by milling or sawing.

The length of the holes along the frame is preferably in the range between 1 mm and 10 mm, more preferably between 3 mm and 7 mm. The greatest depth of a hole corresponds at least to the wall thickness of the frame profile, so that the frame profile is at least partially completely removed to expose an opening in the interior of the frame profile. As the maximum depth of the hole is preferably the depth up to a groove 20 (Fig. 4) for receiving a headband 22 (Fig. 3) of the racket practicable. The width of the hole is preferably in the range between 3 mm and 7 mm.

Also in the case of such holes, it is preferable to provide the opening with a substantially tubular insert or lid, the shape of which may be adapted to the shape of the hole, so that neither dirt nor moisture can get into the interior of the frame profile.

The trough-shaped recesses 12 are preferably formed during molding of the racket frame 4 in the frame profile, for example by providing a corresponding bulge in the mold. Furthermore, it may be preferable to provide in the region of the recesses 12 one or more reinforcing layers in the material forming the frame profile. For example, carbon fiber material, glass or aramid fabric and / or a unidirectional prepreg at an angle of ± 45 ° to the longitudinal frame extension (ie helically in the wall of the frame profile) are incorporated into the racket frame forming frame profile. This is preferably done by superimposing the different layers of frame material and reinforcing material and then rolling the superimposed materials into a "tube", which is then inserted into the molding press and pressed under the action of temperature and pressure to the frame.

The racket according to the invention is particularly advantageous in terms of its improved ball guidance and the ability to give the ball excellent accelerations. The advantageous properties of the racket according to the invention are presumably due to the fact that the bending resistance of the frame profile is considerably lower due to the trough-shaped indentations 12 than in areas of the frame without indentations. As a result, a kind of "joint" is provided, which allows the particularly advantageous ball guide characteristic of the racket. Another advantage of the racket according to the invention lies in its improved damping.

FIGS. 6a and 6b graphically show relative speed values ​​of the racket according to the invention at different frame positions in comparison to conventional rackets. The relative speed is indicated in Figures 6a and 6b as ACOR, where:<maths id="math0001" num=""><math display="block"><mrow><mtext>ACOR = </mtext><mfrac><mrow><msub><mrow><mtext>V</mtext></mrow><mrow><mtext>ball (post_impact)</mtext></mrow></msub><mtext></mtext></mrow><mrow><msub><mrow><mtext>V</mtext></mrow><mrow><mtext>racket (pre_impact)</mtext></mrow></msub></mrow></mfrac><mtext> -1</mtext></mrow></math><img file="EP1557204A2_D0001.tif" /></maths> where V_{ball (post_impact)} the speed of the ball is immediately after the impact of the ball on the string of the racket and V_{racket (pre_impact)} the speed of the bat is just before the ball hits. The marking on the rack, shown diagrammatically on the right in the diagrams according to FIGS. 6a and 6b, indicates the impact position of the ball with respect to the longitudinal axis of the racket passing through the gripping portion. According to FIG. 6a, the ball hits the clothing of the racket slightly laterally of the longitudinal axis, whereas according to FIG. 6b the ball hits the center of the clothing of the racket. On the abscissa, the impact positions of the ball are plotted, the scale each begins on the right with zero, that is, at the end of the handle, and the head of the racket towards the distance in millimeters is indicated. This is easily comprehensible on the basis of the racket shown schematically below in FIGS. 6a and 6b.

The respective uppermost curve (white) in FIGS. 6a and 6b in each case represents the relative speed of a racket according to the invention, which is designated "LM8 ++" in FIGS. 6a and 6b.

In comparison, a conventional "LM 8" racket was tested, ie the same racket, for which the gray curve in Figures 6a and 6b applies, but which has no indentations. The curve appears black in FIGS. 6a and 6b and lies in each case below the white curve for the same bat with indentations.

The lowermost curve in FIGS. 6a and 6b (gray) represents a prior art racquet in approximately the same way as EP 0 676 222 B1, which was mentioned in the introduction to the description. As can be seen from FIGS. 6a and 6b, this racket has a significantly reduced relative speed compared with the racket according to the invention and thus also a comparatively poorer acceleration capacity. This applies both to the lateral impact of the ball (FIG. 6a) and to the central impact of the ball (FIG. 6b) over the entire measuring area along the club head.

In FIGS. 7a and 7b, respectively the contact time or The ball dwell time is shown in milliseconds above the racket position, with ball impact locations being shown in the same manner as in Figures 6a and 6b and again at 7a ball impact points laterally of the racket longitudinal axis and 7b central ball impact points were measured. As can be seen in Figure 7a, the contact time of the racket according to the invention (white line) over the entire measuring range above that of a same racket without indentations (black line) and also almost over the entire measuring range well above that of the conventional racket according to the prior art after EP 0 676 222 B1 (gray line), d. H. the contact time is longer with the bat according to the invention. For a central impact according to the illustration of FIG. 7b, this characteristic is even more pronounced. Here, the contact time of the ball on the club according to the invention (white line) is significantly longer than in the comparison racket without indentations (black line) and even significantly longer than in the racket according to the prior art according to EP 0 676 222 B1 (gray line). This increased residence time or Contact time of the ball on the fabric of the racket according to the invention leads to a significantly improved ball control, so that not only the acceleration of the ball but also the accuracy of the club according to the invention over the prior art is considerably increased.